When a mobile station transmits some kind of data to a core network side, the mobile station issues a request for establishment of a data communication channel to a radio base station (refer to Patent Literature 1). At this point, if a radio resource (frequency bandwidth or the like) does not have free space for which a data communication channel can be established, the radio base station rejects the request for establishment of the data communication channel and then the mobile station tries to issue the request for establishment of the data communication channel at a predetermined period of time later.